2016-12-09T13:34:43ZNew insights into 17th and 18th century glass from Portugal: study and preservationhttp://hdl.handle.net/10362/19089
Título: New insights into 17th and 18th century glass from Portugal: study and preservation
Autor: Coutinho, Inês
Resumo: Early Modern glass from the Iberian Peninsula has - so far - seldom been investigated. The project, combining chemical analysis with a stylistic approach, and focusing on composition and technology, aims to characterise glass objects circulating in the national territory, in an attempt to identify their origins and to eventually bring to light a Portuguese centre of glass production.
The chemical composition of more than 200 glass fragments was determined by means of μ-PIXE down to a level of tens of μg/g. The results obtained allowed one to select some objects to further extend the analysis to the trace and rare earth elements (REE) down to the ng/g level, through the use of LA-ICP-MS. Glass colours and natural hues were studied by means of UV-Vis reflectance spectroscopy and, when necessary, enamels were studied by means of μ-EDXRF and μ- Raman microscopy.
From all the objects analysed, it was possible to conclude that the great majority of the glass dating upto the 17th century, is of a soda-lime-silica type, which indicates a Mediterranean tradition. Venetian or façon-de-Venise shapes were identified, and for some of them a Venetian provenance was confirmed. For other façon-de-Venise shapes, the composition presented differences that led to the conclusion that new façon-de-Venise production centres could be recognised. From the only assemblage containing glass fragments dated to the medieval period, it was possible to attest the
presence of Venetian glass in the Portuguese territory from at least the 14th century.
Additional objects showed particular compositional features, such as high and very high alumina contents for instance, that, as far as it is known, do not match up with any of the known glass production centres in Europe. Allying the stylistic characteristics with the glass chemical composition, allowed one to identify some objects possibly belonging to a Portuguese production.
Several glass fragments belonging to wine bottles were retrieved from archaeological excavations in Lisbon and were chemically characterised. The chemical analysis revealed an HLLA composition for all of them. For some of these fragments it was possible to propose an English provenance. Besides the chemical characterisation, a systematic analysis of the bottle shape was proposed since the shape can be an important factor in determining its chronology.
A small percentage of the fragments were identified chemically as having mixed-alkali compositions, potassium-rich glass, and lead glass compositions. The latter two chemical formulations were found among the assemblages from Lisbon and the objects with these compositions were dated to the 18th century. These constitute evidence that Portugal followed European tendencies in their glass and its compositions.
This is the first systematic chemical characterisation of Early Modern glass circulating in Portugal, providing new insights into trade between Portugal and its trade allies.
As a part of the study, and to prolong the survival of these glass assemblages, simple and low cost optical sensors were developed for the in situ detection of the organic pollutant formic acid, which is emitted by materials usually used in storage and in the display of glass. The detection of the presence of this acid can play an important role in the preservation of this valuable heritage; glass.2016-03-01T00:00:00ZFungal biodeterioration of paper: development of safer and accessible conservation treatmentshttp://hdl.handle.net/10362/18496
Título: Fungal biodeterioration of paper: development of safer and accessible conservation treatments
Autor: Sequeira, Sílvia Oliveira
Resumo: Great part of the History of mankind is registered in the form of documents or works of art on paper support. Paper can be deteriorated due to physical, chemical and biological agents. Within microorganisms, fungi are the major paper biodeteriogens. Throughout history, several toxic methods have been used to prevent and stop fungal deterioration on paper based materials. More recently, a growing concern about environmental and health issues has led to the research on new antifungal alternatives, with lower toxicity. However, the existent antifungal methods and compounds still have drawbacks in terms of efficacy, health hazards, damaging effects on paper, or lack of thorough testing. In this context, the present thesis focused on testing and developing accessible antifungal treatments with low toxicity, which could prevent the long term paper deterioration.
The selection of antifungal compounds was made taking into account the results from a literature review on antifungals used on paper conservation, a survey to paper conservators, and a review of antifungals used in cosmetics and pharmaceutical industries, having as a basic premise their low toxicity. Aspergillus niger, Chaetomium globosum, Cladosporium cladosporioides, Penicillium chrysogenum and Penicillium corylophilum were selected as test fungal species. Fungal growth on paper was evaluated by measuring colonization areas and biomass dry weight determination.
A formulation containing parabens and calcium propionate (PBs+CP) presented the best antifungal activity on paper samples, followed by a formulation containing clotrimazole and calcium hydroxide nanoparticles (CLT+NPs), and ultimately 70% ethanol (70%EtOH).
Before application on cultural heritage materials, conservation treatments have to be thoroughly tested to assess if they can cause any damage on the treated materials in the short and long term. The effects of the tested formulations on paper were evaluated in terms of pH, colourimetry, folding endurance and molecular alterations, using moist heat artificial ageing. Besides plain paper, paper previously biodeteriorated by A. niger was tested in order to evaluate the potential of each compound to prevent further deterioration caused by fungal metabolites. The obtained results on biodeteriorated samples illustrate how tremendously damaging the products excreted by fungi can be in the long term. PBs+CP formulation was the only one capable of preventing long term acidification, loss of folding endurance, and discoloration caused by fungal metabolites, but on the other hand, on plain samples, this formulation caused paper discoloration. CLT+NPs formulation significantly prevented the acidification and loss of folding endurance, although causing a minor discoloration on paper at a long term. 70%EtOH had a mild positive impact in the chemical stabilization of paper and did not cause any paper discoloration.
The information provided in this thesis contributes to a deeper understanding on safer options for preventing and treating paper deterioration by fungi and opens the way for further research in this challenging field of heritage conservation.2016-04-01T00:00:00ZThe perfect paint in modern art conservation: a comparative study of 21st century vinyl emulsionshttp://hdl.handle.net/10362/16840
Título: The perfect paint in modern art conservation: a comparative study of 21st century vinyl emulsions
Autor: Pereira, Ana Isabel Morais Lavrador
Resumo: Contemporary painting places, and will continue to place, several questions about its meaning, its chemical nature, its durability and the best way to preserve it. This research aims at putting together comprehensive data on vinyl based paints, including their components, their properties, their aging behavior and their response to selected cleaning products.
In this project degradation mechanisms of vinyl binders and formulations used in the 20th and 21st century were studied. Stability over time of selected vinyl polymers was assessed through natural indoor and artificially aging. The objective was to enhance knowledge and understanding of vinyl emulsion formulations and their performance over time.
Overall conservation state of pictorial layers namely, adhesion, cohesion and discoloration of selected case studies from the Portuguese artist Julião Sarmento (b.1948) was correlated with the observed molecular level changes studied in laboratory experiments. Sarmento’s paintings were chosen due to conservation concerns (discoloration) on some of his works from the 90’s. Besides, research was carried out to start increasing the knowledge of what can be expected of PVAc based paints in terms of response to conservation treatments namely, surface cleaning.
Artificial aging showed that the most recent formulations which are based on a poly(vinyl acetate), poly(vinyl chloride) and polyethylene terpolymer are less stable when compared to some homopolymer formulations. From the four pigments studied, titanium dioxide rutile and a carbon based black proved to be stabilizers for both types of polymer. The mixture lithopone plus calcium carbonate has showed to have a photocatalytic effect on the binders.
The studied paintings showed to be in an overall good state of conservation except for the paintings created in the 90’s with white glue and a mixture of white lithoponeand calcium carbonate. Discoloration of this white paint seems to be irreversible and ongoing and is still a major concern. The disapearance of the plasticizer was the only change detected. The current works created by Sarmento are expected to be more stable as they were painted using the rutile titanium dioxide.
Immersion/cleaning tests showed that vinyl based paints can be susceptible to water and organic solvents like ethanol as some evidences point to the removal/diffusion of additives from the paint. The observations made point to the need to further proceed in this research field.2015-02-01T00:00:00ZBiological colonization on majolica glazed tiles: biodeterioration, bioreceptivity and mitigation strategieshttp://hdl.handle.net/10362/15765
Título: Biological colonization on majolica glazed tiles: biodeterioration, bioreceptivity and mitigation strategies
Autor: Coutinho, Mathilda Amélia Gonçalves Larsson Dias
Resumo: The impact of microbial activity on the deterioration of cultural heritage is a well-recognized global problem.
Glazed wall tiles constitute an important part of the worldwide cultural heritage. When exposed outdoors, biological colonization and consequently biodeterioration may occur. Few studies have dealt with this issue, as shown in the literature review on biodiversity, biodeterioration and bioreceptivity of architectural ceramic materials.
Due to the lack of knowledge on the biodeteriogens affecting these assets, the characterization of microbial communities growing on Portuguese majolica glazed tiles, from Pena National Palace (Sintra, Portugal) and another from Casa da Pesca (Oeiras, Portugal) was carried out by culture and molecular biology techniques. Microbial communities were composed of microalgae, cyanobacteria, bacteria and fungi, including a new fungal species (Devriesia imbrexigena) described for the first time.
Laboratory-based colonization experiments were performed to assess the biodeterioration patterns and bioreceptivity of glazed wall tiles produced in laboratory. Microorganisms previously identified on glazed tiles were inoculated on pristine and artificially aged tile models and incubated under laboratory conditions for 12 months. Phototrophic microorganisms were able to grow into glaze fissures and the tested fungus was able to form oxalates over the glaze. The bioreceptivity of artificially aged tiles was higher for phototrophic microorganisms than pristine tile models.
A preliminary approach on mitigation strategies based on in situ application of commercial biocides and titanium dioxide (TiO2) nanoparticles on glazed tiles demonstrated that commercial biocides did not provide long term protection. In contrast, TiO2 treatment caused biofilm detachment. In addition, the use of TiO2 thin films on glazed wall tiles as a protective coating to prevent biological colonization was analysed under laboratorial conditions. Finally, conservation notes on tiles exposed to biological colonization were presented.2015-04-01T00:00:00Z